Mo-doped and undoped GeGaAs layers have been deposited by the thermionic vacuum arc (TVA) method, an alternative, fast plasma deposition technique. The thicknesses of the deposited layers were identical. The surface, mechanical, and optical properties of the deposited layers were studied to determine the influence of Mo doping on GeGaAs. The transparency of GeGaAs was shifted towards the near-infrared region by Mo doping. Bandgap values shifted by approximately 0.3 eV. In other words, the bandgap value of Mo-doped GeGaAs was nearly equal to that of GaAs materials. The average roughness and grain size of the Mo-doped material were smaller than for the GeGaAs layer. The particle distributions of the Mo-doped and undoped GeGaAs were almost perfect Gaussians. However, the mean height of the Mo-doped GeGaAs grains was six times that for undoped GeGaAs. The surface was homogeneous. The Mo-doped layer showed greater absorbance than the GeGaAs material. The produced Mo-doped sample showed hybrid properties.